1. Field of the Invention
The present invention relates to a focal plane shutter for cameras which is used for single-lens reflex cameras, mirrorless single-lens cameras, or the like.
2. Description of Related Art
Focal plane shutters for cameras include: a focal plane shutter which is provided with only a single shutter blade; and a focal plane shutter which is provided with two shutter blades called a first blade and a second blade respectively. And, the focal plane shutter including only a single shutter blade is usually formed as a focal plane shutter in which shooting is started with an exposure aperture fully opened and shooting is finished by closing the exposure aperture through the shutter blade. Also, the focal plane shutter including two shutter blades is usually formed as a focal plane shutter in which shooting is started by starting to open an exposure aperture through the first blade and shooting is finished by completely closing the exposure aperture through the second blade. However, it is known that there is also a focal plane shutter including two shutter blades which is formed as a focal plane shutter in which, as often as shooting is performed, a user can choose between: shooting performed in such a manner; and shooting that is started with an exposure aperture fully opened and is finished by closing the exposure aperture through the second blade.
In each of these focal plane shutters, a shutter blade runs by a rotation of a driving member, and a helical torsion coil spring (which is called “driving spring” below) is usually used as a driving source for driving the driving member in shooting. As a result, when shooting is finished, the driving member has to be rotated to its cocking position against the biasing force of the driving spring, and, just before next shooting is started, the driving member has to be kept in its shooting-operation-starting position against the biasing force of the driving spring. And, there are structures which are called locking-type structure and direct-type structure respectively as a structure for keeping the driving member in such a position. Japanese Patent KOKAI No. 2003-66507 discloses a direct-type focal plane shutter which is provided with two shutter blades.
As described also in Japanese Patent KOKAI No. 2003-66507, a conventional direct-type focal plane shutter is formed in such a way that: an electromagnet is fitted to the shutter-base-plate side plane of a support plate which is placed with the plate planes of the support plate parallel to a shutter base plate; and a printed wiring board is fitted on the other side plane of the support plate. And, the printed wiring board not only is provided with a wiring pattern but also is equipped with a condenser, as disclosed in Japanese Patent KOKAI No. 2002-139770 for example but not disclosed in Japanese Patent KOKAI No. 2003-66507. Also, as known publically, the electromagnet is provided with two terminal pins around which the both ends of a coil are wounded respectively, the two terminal pins penetrate through holes provided on the printed wiring board, and the both ends of the coil are soldered to the wiring pattern of the printed wiring board.
On the other hand, as described in Japanese Patent KOKAI No. 2003-66507, the driving member includes an iron piece member, and the driving member is rotatably fitted to a shutter base plate between the shutter base plate and the support plate. And, just before shooting is started, the electromagnet attracts and holds the iron piece member, so that the driving member is kept in its shooting-operation-starting position against the biasing force of the driving spring. Afterward, the driving member is rotated by the biasing force of the driving spring by demagnetizing the electromagnet. The present invention relates to a direct-type focal plane shutter in which such a conventional structure is improved and which includes at least one shutter blade.
Recently, the appearance of mirrorless single-lens cameras accelerates downsizing of single-lens cameras also including single-lens reflex cameras. As a result, a demand to downsize or to thin the whole of a unit with respect to focal plane shutters built into these cameras has been grown more than ever. However, the focal plane shutters have been downsized or made to have a compact size to a considerable extent up to now, so that it has become very difficult to downsize each of components of the focal plane shutters, and an effort to downsize these components in the order of 0.1 mm or less has been actually made.
Now, most of components except shutter blades are intensively fitted to a predetermined area located on the lateral side of an opening for the optical path of light from an object in the shutter base plate in the units of focal plane shutters, as known publically. As a result, the height of shutter unit from a plane of the shutter base plate becomes extremely high only on that area. Accordingly, in the case where the unit is downsized, the height of shutter unit from a plane of the shutter base plate on that area to which these components is intensively fitted has to be lowered somehow or other, first of all. However, downsizing of each of components for focal plane shutters has been performed up to now as described above, so that another ingenuity for downsizing in the view of structures of focal plane shutters is needed.
The present invention is made in order to solve such a problem. The objective of the present invention is to offer a focal plane shutter for cameras: in which the height of shutter unit from a plate plane of a shutter base plate is lowered by improving such a conventional structure as an electromagnet is fitted on the shutter-base-plate side plane of a support plate and a printed wiring board is fitted on the other side plane of the support plate, the support plate being provided while a plate plane of the support plate is parallel to the shutter base plate; and which includes at least one shutter blade.